The Minnesota Orchestra moved with what seemed glacial slowness to replace longtime concertmaster Jorja Fleezanis, who departed in 2009 after a distinguished 20-year tenure. But when finally the orchestra, from an impressive field, chose Erin Keefe as Fleezanis' successor, it chose well.

Keefe has been a presence since taking up her duties as the orchestra's 19th concertmaster in September, making her mark in works as dissimilar as Strauss' brash "Ein Heldenleben" and Brahms' elegiac Clarinet Quintet (with the chamber ensemble Accordo). But only now, with a superlative performance in Beethoven's Violin Concerto on an all-Beethoven Sommerfest program led by Osmo Vänskä, has her stature become fully apparent. She is an extraordinary artist -- a bright new star in the Twin Cities sky.

A Massachusetts native, the 30-something Keefe (now living in St. Paul) is a product of Philadelphia's Curtis Institute and New York's Juilliard School, and has all the musical sophistication and technical polish her pedigree would imply. But she is more than her résumé. Her playing seems to reconcile opposites, combining stillness and exuberance, soberness and sublimity -- qualities to which Beethoven responds gratefully.

Keefe's performance Thursday, entirely from memory, was a double debut: her first appearance as concerto soloist with her Minnesota colleagues and, more remarkably, her first outing anywhere in Beethoven's singular concerto. Yet there was nothing generic, nothing merely accurate. She negotiated Fritz Kreisler's wickedly difficult cadenzas with seeming ease, treating them less as occasions for virtuoso display than as opportunities to dig deeper into Beethoven's musical materials. And the goose-bump moment just after the first-movement cadenza, when at last the soloist plays the work's opening theme, has never seemed more of a consummation.

The concerto was framed by two works more representative of Beethoven's middle period: the "Eroica" Symphony and the "Coriolan" Overture. Vänskä's almost pugilistic "Eroica" is a known quantity -- his recording with the orchestra ranks among the signature achievements of their partnership -- but it has rarely sounded as gutsy as it did Thursday in the University of Minnesota's compact, bass-friendly Ted Mann Concert Hall (where Sommerfest is encamped during Orchestra Hall's makeover).

Launched abruptly, while the audience was still applauding, the opening Allegro seethed; the Finale, often underestimated, brought a sense of cosmic play. And "Coriolan," one of those drama-compressing Beethoven overtures that overshadows the work it was meant to preface, raged mightily.